The conventional water-soluble coolant used in association with machine tools is relatively costly, and an attempt is made to reuse same not only to reduce the overall cost of purchasing such coolant, but also to avoid the disposal problem associated with contaminated coolant. During use, the coolant becomes contaminated not only with solid contaminants, such as machine chips and the like, but also due to its contact with typical oils such as hydraulic fluids used in association with machines, such oils being referred to as "tramp oil".
At the present time, various cleaning processes and apparatus have been proposed for removing solid contaminants, but such apparatus are normally rather large, complex and costly, and as such are typically suited only for use in situations involving large quantities or batches of contaminated coolant. Further, these known apparatus are normally designed for use in situations where solids are the significant contaminants which are to be removed. However, such apparatus are not suitable for use in all applications since, in many manufacturing operations, the contamination of coolant with tramp oil is a more significant problem.
When significant quantities of tramp oil collect and contaminate the coolant, such oil can effect the desirable properties of the coolant during use. Further, such tramp oil tends to become rancid so that further use of the coolant is highly unsatisfactory.
Thus, it is an object of this invention to provide an improved system and method for effecting removal of oil from coolant to permit reuse of the coolant, which improved system and method is particularly desirable for use with batches of contaminated coolant, and is highly effective in providing an operation which is advantageous in comparison to prior apparatus.
In the improved system and method of the present invention, a batch of contaminated coolant is deposited into a tank, with the coolant preferably being passed through a filter during the depositing step so as to effect removal of solids. Once the contaminated coolant has been deposited into the tank, the coolant is bubbled by injecting several streams of air into the bottom of the tank. This creates bubble streams which pass upwardly through the coolant toward the surface and, during this passage, effect separation of the oil so that it rapidly rises to the coolant surface. At least one of the bubble streams is created by a nozzle or orifice member which differs from other orifice members so that the bubbles of this one stream are smaller than the bubbles in other streams. This causes agitation vertically through the mass of coolant, but also differential agitation at the surface, whereby the tramp oil which rapidly rises to the surface tends to congregate within a small surface area disposed directly over the small bubble stream, thereby facilitating removal of the separated oil.
Other objects and purposes of the invention will be apparent to persons familiar with this industry upon reading the following specification and inspecting the accompanying drawings.